1. Field of the Invention
The present invention relates to a sealing mechanism for sealing a vacuum chamber, and more particularly to a sealing mechanism for sealing a vacuum chamber formed in the semiconductor producing apparatus to be shut down from its exterior.
2. Description of the Related Art
In general, the semiconductor producing apparatus of this kind is maintained vacuumized and highly pure in air for producing such products because dusts and other foreign materials are detrimental to wafers and other semiconductor materials in the process of producing the semiconductor producing apparatus. The semiconductor producing apparatus is usually required to be operated by some kinds of driving mechanism such as a manipulator driven by a drive shaft to handle semiconductor devices, LCD base plates and other objects to be treated. The drive shaft has axial portions extending inside and outside of a vacuum chamber formed in the semiconductor producing apparatus. This means that the gaps between the axial portions of the drive shaft and the other parts"" around the axial portions of the drive shaft are required to be tightly sealed to have the vacuum chamber maintained at a constant vacuum level.
In recent years, meanwhile, the process of producing semiconductors has remarkably been progressed to obtain more excellent performance, higher density and integration for the products. The process, however, tends to have a relatively low productivity as compared with other industrial products. This is due to the fact that dusts and foreign materials detrimental to wafers and other semiconductor materials are apt to enter the vacuum chamber of the semiconductor producing apparatus. The dusts and foreign materials which may cause inferior products are each made of a particle generally larger than the thickness of an insulator layer to be turned into a semiconductor. At the present time, strenuous efforts continue to be made for reducing to as a lowest level as possible such dusts and foreign materials each having a size larger than the thickness of the insulator layer. These strenuous efforts have not yet become successful.
The typical conventional semiconductor producing apparatus is partly shown in FIG. 15 and FIG. 16 and comprises a manipulator 210 drivably installed in the vacuum chamber 261 of the semiconductor producing apparatus which is vacuumized through an aperture 201 formed in the wall of the semiconductor producing apparatus.
The manipulator 210 is shown in FIG. 15 and FIG. 16 as having a drive shaft 250 which is rotatably supported on a support member 240. The wall portion 202 of the semiconductor producing apparatus is formed with a hole 202a having the support member 240 fixedly received therein. The drive shaft 250 shown in FIG. 15 has a forward end portion extending in the vacuum chamber 261 to pivotally support first and second arms 213 and 214, and a handling member 215 operatively coupled with the first and second arms 213 and 214 so that the handling member 215 can be operated to handle semiconductor devices, LCD base plates and other objects to be treated. Also, the drive shaft 250 has a rear end portion extending in the atmosphere 260 and drivably connected with driving means constituted by an electric motor and reduction gears which are not shown in the drawings.
The drive shaft 250 is shown in FIG. 16 as comprising a first cylindrical shaft 230 rotatably received in the support member 240 through bearings 216a and a second cylindrical shaft 220 rotatably received in the first cylindrical shaft 230 through bearings 216b. 
One typical example of the conventional sealing mechanisms is also shown in FIG. 16 to comprise a first group 218 of magnetic fluid seals axially arranged between the support member 240 and the first cylindrical shaft 230, and a second group 219 of magnetic fluid seals axially arranged between the first and second cylindrical shafts 230 and 220. The two groups 218 and 219 of magnetic fluid seals can function to maintain the vacuum chamber 261 in a hermetically sealed state, resulting in the fact that dusts and foreign materials, i.e., fine particles generated from frictional contacts between elements or parts outside of the vacuum chamber 261 can be prevented from entering the vacuum chamber 261.
The conventional sealing mechanism mentioned in the above is of a performance having a resistant pressure of 0.2 atmospheric pressure for each of the magnetic fluid seals 218 and 219. From this reason, the conventional sealing mechanism is required to comprise a plurality of magnetic fluid seals 218 axially disposed in a series between the support member 240 and the first cylindrical shaft 230, and a plurality of magnetic fluid seals 219 also axially disposed in a series between the first and second cylindrical shafts 230 and 220 as described in the above.
The above known sealing mechanism, however, encounters such a problem that the dusts and foreign materials cannot fully be prevented from entering the vacuum chamber and that the vacuum chamber thus cannot be maintained at a constant vacuum level.
It is, therefore, an object of the present invention to provide a sealing mechanism suitable for sealing a vacuum chamber formed in the semiconductor producing apparatus.
It is another object of the present invention to provide a sealing mechanism having an excellent sealing performance to seal a vacuum chamber formed in the semiconductor producing apparatus.
According to the first aspect of the present invention there is provided a sealing mechanism for sealing a vacuum chamber formed in the semiconductor producing apparatus, comprising: a rotation shaft driven to be rotatable around its own axis and having an outer surface in the form of a cylindrical shape; a support member intervening between the vacuum chamber and the atmosphere and rotatably supporting the rotation shaft to have the rotation shaft received therein, the support member having an inner surface in the form of a cylindrical hollow shape and first and second axial ends respectively extending in the atmosphere and the vacuum chamber, the inner surface of the support member being larger in diameter than the outer surface of the rotation shaft, the support member being formed with a first fluid passageway having a first end and a second end and a second fluid passageway having a first end and a second end open toward the vacuum chamber; first and second seal rings positioned between the rotation shaft and the support member in axially spaced-apart relationship with each other to hermetically seal the gap between the rotation shaft and the support member under the state that the first seal ring is located in the neighborhood of the first axial end of the support member and remote from the second axial end of the support member and that the second seal ring is located in the neighborhood of the second axial end of the support member and remote from the first axial end of the support member, the rotation shaft, the support member, and the first and second seal rings collectively forming a first fluid chamber held in communication with the first fluid passageway through the first end of the first fluid passageway; an air sucking unit having a port held in communication with the second end of the first fluid passageway to maintain the pressure of the first fluid passageway at a level between the atmospheric pressure and the inner pressure of the vacuum chamber; a third seal ring positioned between the rotation shaft and the support member in axially spaced-apart relationship with the second seal ring between the second seal ring and the extension plane radially inwardly extending and flush with the second axial end of the support member to hermetically seal the gap between the rotation shaft and the support member, the rotation shaft, the support member, and the second and third seal rings collectively forming a second fluid chamber held in communication with the second fluid passageway through the first end of the second fluid passageway; and a fluid filter disposed on the portion of the support member exposed to the vacuum chamber to cover the second end of the second fluid passageway.
According to the second aspect of the present invention there is provided a sealing mechanism as set forth in claim 1 in which the support member is formed with an additional first fluid passageway and an additional second fluid passageway.
According to the third aspect of the present invention there is provided a sealing mechanism for sealing a vacuum chamber formed in the semiconductor producing apparatus, comprising: a first rotation shaft driven to be rotatable around its own axis and having an outer surface in the form of a cylindrical shape; a second rotation shaft driven to be rotatable around its own axis and rotatably receiving therein the first rotation shaft, the second rotation shaft having an inner surface in the form of a cylindrical hollow shape, first and second axial ends respectively extending in the atmosphere and the vacuum chamber, and an outer surface in the form of a cylindrical shape, the inner surface of the second rotation shaft being larger in diameter than the outer surface of the first rotation shaft, the second rotation shaft being formed with a first fluid passageway having first and second ends respectively open at the inner and outer surface of the second rotation shaft and a second fluid passageway having first and second ends respectively open at the inner and outer surface of the second rotation shaft; a support member intervening between the vacuum chamber and the atmosphere and rotatably supporting the second rotation shaft to have the second rotation shaft received therein, the support member having an inner surface in the form of a cylindrical hollow shape and first and second axial ends respectively extending in the atmosphere and the vacuum chamber, the inner surface of the support member being larger in diameter than the outer surface of the second rotation shaft, the support member being formed with a third fluid passageway having a first end and a second end and a fourth fluid passageway having a first end and a second end open toward the vacuum chamber; first and second seal rings positioned between the first and second rotation shafts in axially spaced-apart relationship with each other to hermetically seal the gap between the first and second rotation shafts under the state that the first seal ring is located in the neighborhood of the first axial end of the second rotation shaft and remote from the second axial end of the second rotation shaft and that the second seal ring is located in the neighborhood of the second axial end of the second rotation shaft and remote from the first axial end of the second rotation shaft, the first and second rotation shafts and the first and second seal rings collectively forming a first fluid chamber held in communication with the first fluid passageway through the first end of the first fluid passageway; a third seal ring positioned between the first and second rotation shafts in axially spaced-apart relationship with the second seal ring between the second seal ring and extension plane radially inwardly extending and flush with the second axial end of the second rotation shaft to hermetically seal the gap between first and second rotation shafts, the first and second rotation shafts and the second and third seal rings collectively forming a second fluid chamber held in communication with the second fluid passageway through the first end of the second fluid passageway; fourth and fifth seal rings positioned between the second rotation shaft and the support member in axially spaced-apart relationship with each other to hermetically seal the gap between the second rotation shaft and the support member under the state that the fourth seal ring is located in the neighborhood of the first axial end of the support member and remote from the second axial end of the support member and that the fifth seal ring is located in the neighborhood of the second axial end of the support member and remote from the first axial end of the support member, the second rotation shaft, the support member, and the fourth and fifth seal rings collectively forming a third fluid chamber held in communication with the first fluid passageway through the second end of the first fluid passageway and the third fluid passageway through the first end of the third fluid passageway; an air sucking unit having a port held in communication with the second end of the third fluid passageway to maintain the pressure of the third fluid passageway at a level between the atmospheric pressure and the inner pressure of the vacuum chamber; a sixth seal ring positioned between the second rotation shaft and the support member in axially spaced-apart relationship with the fifth seal ring between the fifth seal ring and the extension plane radially inwardly extending and flush with the second axial end of the support member to hermetically seal the gap between the second rotation shaft and the support member, the second rotation shaft, the support member, and the fifth and sixth seal rings collectively forming a fourth fluid chamber held in communication with the second fluid passageway through the second end of the second fluid passageway and the fourth fluid passageway through the first end of the fourth fluid passageway; and a fluid filter disposed on the portion of the support member exposed to the vacuum chamber to cover the second end of the fourth fluid passageway.
According to the second aspect of the present invention there is provided a sealing mechanism as set forth in claim 3 in which the second rotation shaft is formed with an additional first fluid passageway and an additional second fluid passageway, and the support member is formed with an additional third fluid passageway and an additional fourth fluid passageway.